Infrared quartz heater



1969' R. R. POOLE 3,461,275

' INFRARED QUARTZ HEATER v Filed Jan. 26, 19 68 a Sheets-Shani Aug. 12,1969 R. R. POOLE 3,461,275

v INFRARED QUARTZ HEATER Filed Jan. 26. 1968' v a Sheets-Sheet z x/ 1 MYAug. 12, 1969 R. R. POOLE INFRARED QUARTZ HEATER Filed Jan. 26, 1968United States Patent York Filed Jan. 26, 1968, Ser. No. 700,763 Int. Cl.11-10% 3/10 US. Cl. 219-553 10 Claims ABSTRACT OF THE DISCLOSURE Thequartz heater of the present invention comprises a coiled electricalresistance wire inside a quartz tube and capped at each end by an endcap. The coils may have a variable pitch, to generate less radiant heatenergy at the center of the heater than adjacent the end caps. Thecemented juncture of the end caps and quartz tube has a metallic fillermesh interposed between the tube and the end cap; the filler mesh isbelieved to lower the failure rate of the quartz heater. The terminus ofresistance wire itself extends through the base of each end cap and isformed into the terminal leads for the quartz heater.

The present invention relates to a high intensity heat radiating unitand more particularly to a quartz heater constructed to withstand thesevere environmental stresses imposed by rotary process rolls.

The usual quartz infrared heater consists essentially of a resistancewire heating element, appropriate electrical connections to the heatingelement and a surrounding quartz envelope or tube. Typically the quartztube is mounted in ceramic end caps through which the electricalconnections pass, the caps serving to mount and attach the heater in thedesired position on a structural support.

The art has long since recognized the extent to which quartz heaters ofthis nature are subject to breakage; the quartz tube is fragile. Thisproblem is particularly severe when thermal cycling (i.e., the heaterbeing turned on and 0d at frequent intervals) is associated withconsiderable vibration. In point of fact conventional quartz heatersused as the heating element for thin wall rotary process rolls haveshown a distressingly short life. The bulk of the failures occur fromfracture at the juncture of the quartz envelope with the ceramic endcaps and from electric failure due to weakness at the terminationstructure of the heater wire.

Accordingly, the object of the present invention is to provide animproved high intensity quartz heater of long operating life.

A further object of the present invention is to provide for an improvedjuncture of the quartz envelope with the end caps in a quartz heaterassembly.

Still another object is to provide a quartz heater terminal lead ofimproved construction.

An additional object is to provide a quartz heater with a simplified yeteffective mounting structure,

Further objects and the advantages of the present invention will beapparent from the description thereof which follows.

Reference is now made to the attached drawings wherein:

FIG. 1 is an exploded view of the components of the quartz heater;

FIG. 2 is a side view of the quartz heater during the assembly thereof;

FIG. 3 is a partial section showing the quartz heater in a late stage ofassembly.

FIG. 4 is a side view of the quartz heater.

FIG. 5 is a sectional View of the quartz heater shown in FIG. 4.

FIG. 6 is a side view of a dual heater assembly.

3,461,275 Patented Aug. 12, 1969 FIG. 7 is an end view of thin wallrotary process roll with portions broken away.

FIG. 8 is a side section of the precess roll taken along the lines 8-8in FIG. 7.

' The quartz heater 10 of the present invention is formed from a pair ofend caps 12, a quartz tube 14 and a heater element 16 in the form of acoiled resistance wire. Also present is a metal filler mesh 18 oftemperature resistant metal, e.g., stainless steel or nickel, which alsois highly resistant to oxidation at the elevated operating temperaturesof quartz heater 10. A ceramic cement 20 serves as an adhesive to bondthe juncture of metallic filler mesh 18, end caps 12 and quartz tube 14as shown in FIG. 5.

End cap 12 is formed by a circular base 22 and a cylindrical shoulder 24upstanding therefrom. A circumferential circular groove 26 is providedon shoulder 24 to accommodate a crescent type metallic (e.g., stainlesssteel) snap ring 28 (shown on FIG. 8), the snap ring 28 being employedin the installation of quartz heater 10 in an overall heater assembly.The base 22 of end cap 12 is provided with a pair of apertures 30through which the electrical leads to heater element 16 may be passed.

Advantageously the present quartz heater construction uses the heatingelement wire itself for the high temperature lead wire. As shown in FIG.2 the resistance wire forming heater element 16 has a coiled centralportion 31 and straight or at least noncoiled end portions 32. The endportion 32 is passed through one of the double apertures 30 in the base22 of end cap 12, then doubled back on itself, the doubled back segmentbeing passed back through end cap 12 by way of the other aperture 30.The terminus of end portion 32 is now looped or hooked around itself(shown in FIG. 2) with loop 34 closely adjacent the coiled centralportion 31 of heater element 16. Element 16 is then inserted into endcap 12 so that loop 34 and the coil itself set down into cap 12 adjacentthe base 22 thereof (as illustrated in FIG. 5). The doubled backterminal p rtion 32 is now twisted, e.g., five turns per inch, as shownin FIGS. 4, 5 to provide an anchored, integral terminal lead wire 33 forthe heating element 16. The lead wire 33 is suitably insulated as by theceramic fish spine insulators 36 shown on FIG. 6. A terminal 38 may bewelded or otherwise secured to the free end of lead wire 33. Desirablytwo or more quartz heater units can be associated in series by weldingor otherwise attaching their lead wires together as at 40, in the doubleunit structure shown in FIG. 6.

At some stage during formation of lead wires from end portions 32, thefiller mesh 18 and quartz tube should, of course, be placed aroundheater element 16 and inside end caps 12. FIGS. 2 and 3 illustrating therelationship of these component parts during assembly of quartz heater10. A preferred assembly technique is to form completely a twisted leadwire 33 at one end, cement the tube, mesh and cap together at that end,then repeat the assembly operation at the other end, i.e.,

(1) !Place the components in proper juxtaposition.

(2) Form the doubled back, looped resistance wire end (as shown in FIG.3).

(3) Set quartz tube 14 and filler mesh into end cap 12, then twist theexposed end portion 32 and cement.

(4) Add insulators 36, and weld on terminal 38. Desirably the completedquartz heater 10 has the axis line of apertures 30 of one end cap 12disposed at a right angle to the axis line of the apertures of the otherend cap.

In any event a conventional adhesive ceramic heat resistant cement 20 isplaced at the juncture of quartz tube 14, filler mesh 18, and cap 12,then set, e.g., by heating at F. for about six hours to adhesively bondtogether the end cap, the filler mesh and the quartz tube.

The low failure rate of present quartz heater structure seemsattributable to several features. Allusion has already been made to useof the heating element wire itself as the terminal leads. This featureis desirable, aside from any saving in cost by elimination of theseveral pieces of hardware otherwise used to affix separate lead wiresto the heater element. The integral character of the terminal leadpermits a more compact heater construction and avoids possibility ofburnout at the juncture of the lead wire to the heating element wire.Another feature of construction significant for low failure rate is themetal filler mesh 18. Presence of metal filler mesh 18 seems to reducethe incidence of fracture of the quartz tube where it enters an end cap.It is theorized that submitting the quartz heater to extensive vibrationcauses breakdown of the ceramic cement joining the quartz tube and endcap, with loss of cement particles. Thereafter vibration causes thequartz tube to move separately from the end cap, which in turn causesthe tube surface to craze; eventually the tube fractures. The mesh offiller 18 acts to trap the adhesive cement in the mesh openings, andseems also to absorb some of the vibrational energy thereby preventingbreakup of the cement and subsequent tube fracture.

Filler mesh 18 may be of several forms such as woven wire, knitted wireor expandes metal, the lattermost being preferred. Thus a sheet ofexpanded (or woven) wire mesh cut to proper size is rolled into atubular piece of appropriate diameter without overlapped ends. Theheight of the tubular piece is sufficient for filler mesh piece 18 toextend beyond end cap 12 (e.g., 0.25 inch) as shown in the drawing.

Repeated allusion has been made to use of the present quartz heaterstructure for the heating elements of thin walled process rolls. Such astructure is illustrated in FIGS. 7 and 8 wherein a rotary thin walledprocess roll 100 is radiantly heated by multiple quartz heaters mountedin a heater assembly support 102. Support 102 comprises a hollowcylinder 104 carrying a heat insulator 106. A plurality of spiders 108secure cylinder 104 to a cylindrical sleeve 110 surrounding a supportingshaft 112. Shaft 112 is of course supported at one or both endsindependently of rotating process roll 100 and of the roll drivemechanism. There the heating assembly 102 as a whole is disposed in astationary position inside rotating process roll 100. Present on thecylinder 104 at or adjacent its terminal ends are rings 114. The spacingbetween rings 114 corresponds closely to the overall length of quartzheaters 10 so that the heaters may be mounted therein. The terminals 38of one polarity from each quartz heater 10 extend to a bolted connectionon one electrode connector 130 at apertures 134. The terminals ofopposite polarity connect to electrode connector 128, as is shown inFIGS. 7, 8. The electrodes 122 themselves are spaced apart inside shaft112 by bushings 124 and an end bushing 126. The central electrode 122 isjoined at 132 to connector 130 while the outside electrodes are joinedto connector 128.

The heater assembly actually illustrated in FIGS. 7, 8 is for a twelvepack, using six heater pairs 120, each pair being formed as shown inFIG. 6. Six pairs of apertures 116 are provided in the rings 114 oncylinder 104. Insertion of the quartz heaters 10 on the heater assemblysupport is relatively facile, since the end caps 12 fit closely insidethe apertures 116. The heaters are slipped into apertures 116, thenretaining crescent rings 28 are placed in the groove 26 (one at each endcap) to lock the quartz heater 10 in place. These ring retainers 28 areto restrain longitudinal movement of heater 10 in either direction. Thefit of quartz heater 10 in apertures 116 is suflicient to preventdisengagement from rings 114, whether heater 10 is hot or cold, allowingfor the differential thermal expansion and contraction characteristicsof support 102 and heater assembly 10. Pairing heaters 10 in a seriesconnection as shown in FIG. 6 permits all of the electrical connectionsto the heater assembly to be at whichever end may be most convenient tothe power supply.

Process rolls such as the roll shown in FIGS. 7 and 8 have relativelyrigid heating requirements. The present quartz heater construction andheater assembly are particularly well adapted to heat thin wall rotaryprocess rolls. For example they may be employed as the roll heatingelements in the system disclosed by copending application Ser. No.475,206 of John H. Troll, filed July 26, l965, now Patent No. 3,369,106,issued Feb. 13, 1968. Alluded to in that application is the desirabilityof controlling the axial thermal profile of the process roll.Inescapably, a process roll such as roll 100 loses more heat byradiation and convection adjacent the roll ends (end effect) than fromthe mid regions of the roll. A particular advantage of the presentquartz heater construction is the possibility therein for providing anon-uniform heat output from the heater by appropriate construction ofheater element 16.

As illustrated in the drawing, heater element 16 is a coiled resistancewire. Normally the coiled central portion 31 has coils of uniform pitchthroughout, with the adjacent convolutions being closely spaced so as toprovide maximum (uniform) output per running inch of heater element. Forinstallation of quartz heater 10 in process rolls, however, such aresistance wire is relatively disadvantageous because end elfects createan axial temperature differential along the roll; the roll is hotter inthe center than adjacent either end. However, if the resistance wire ofheater element 16 is constructed with a variable pitch in coiled centralportion 31, the nonuniformity of heat output from the wire coil can bepredetermined so as to flatten out the temperature differential alongthe roll. Thus, in one preferred embodiment heater element 16 isconstructed with the coil convolutions in the middle 17 of centralportion 31 spaced farther apart than the coils adjacent straight ends 32of the heater element 16. Thereby, the temperature profile of processroll 100 is flattened out. Still other pitch variations can providespecial heating effects. Thus quartz heater 10 may be built to emit 50%of its radiation from of the heater length and 50% from the remainingWhile particular embodiments of the invention have been illustrated anddescribed, it will be obvious that changes and modifications may be madewithout departing from the invention and it is intended to cover in theappended claims all such modifications and equivalents as fall withinthe true spirit and scope of this invention.

What is claimed is:

1. A quartz heater comprising a quartz tube, a ceramic end cap at eachend of said tube, and a resistance heating element inside said tube withthe terminal leads thereof extending out through said caps and acylindrical metal filler mesh interposed between the quartz tube and theend cap at the juncture of the tube and cap, the juncture of tube,filter mesh and cap being adhesively bonded by a heat resistant ceramiccement.

2. The heater of claim 1, wherein the metal filler mesh is a piece ofrolled, expanded metal.

3. The heater of claim 1, wherein the lead wires thereto are formed fromthe heater element.

4. The apparatus of claim 1, wherein said coiled resistance wire has apredetermined nonuniform pitch whereby the energy emitted by said heatervaries axially thereof.

5. A quartz heater comprising a quartz tube, a ceramic end cap at eachend of said tube and secured thereto, and a resistance heating elementinside said tube with the terminal leads thereof extending out throughsaid caps, each cap having a pair of apertures in the base thereof, theresistance heating element being a coiled resistance wire with noncoiledterminal end portions thereon, the noncoiled end portion passing outfrom the cap through one base aperture thereof and doubling back inthrough the other base aperture thereof with the doubled back wire endportion outside the cap being twisted, said exposed twisted wire endportions being said terminal leads.

6. The apparatus of claim 5, wherein the doubled back end portion ofsaid resistance wire terminates in a loop hooked around said resistancewire inside the cap.

7. The apparatus of claim 5, wherein the said coiled resistance wire hasa predetermined nonuniform pitch whereby the energy emitted by saidheater varies axially 5 thereof.

8. The apparatus of claim 5, wherein a cylindrical metal filler mesh isinterposed between the quartz tube and the end cap at the juncture ofthe tube and cap, the juncture of tube, filter mesh and cap beingadhesively bonded by a heat resistant ceramic cement. 9. The apparatusof claim 1, wherein each end cap has a circular groove on the peripherythereof, said grooves being adapted to placement therein of a retainerring for ultimate installation.

10. The apparatus of claim 7, wherein the mount for said quartz heatercomprises a cylindrical support means having apertured ring membersaround the periphery thereof adjacent each end, the apertures on eachring being aligned, said quartz heater end caps fitting into a pair ofaligned apertures and retainable therein by place ment of a retainingring in the circular groove of each end cap.

References Cited UNITED STATES PATENTS 1,110,532 9/1914 Byce 338-2182,535,268 12/1'950 Coats 219553 X 2,596,837 5/1952 Calvert 219-553 X2,690,491 9/1954 Calvert 338-236 2,957,154 10/1960 Strokes 219-553 X3,345,448 10/1967 Malkin 1325 VOLODYMYR Y. MAYEWSKY, Primary ExaminerUS. Cl. X.R.

